实现动态加载一个 JavaScript 资源

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实现动态加载一个 JavaScript 资源

 关键字：
        onreadystatechange
        loaded 
        complete 
        readyState
        onerror

var script = document.createElement(“script”);

var head = document.getElementsByTagName(“head”)[0];


script.type = “text/javascript”;

script.src = “//i.alicdn.com/resource.js”;


// 绑定资源加载成功事件

script.onreadystatechange = function( ){

// 判断资源加载状态是否为加载成功或加载完成

if(/^(loaded|complete)$/. test (script.readyState)  ) {

script.onreadystatechange = null;

. . . .

}

};


// 绑定资源加载失败事件

script.onerror = function( ) {

. . . .

};


head.insertBefore (script , head.firstChild)